A semiconductor memory device has a sense amplifier designed to detect a slight differences between the potentials on two mutually associated bit lines of a memory array which consists of a multiplicity of memory cells. Such a differential voltage between the two bit lines is detected upon amplification by the sense amplifier. Such a sense amplifier basically consists of two series combinations of transistors provided between a supply voltage and a ground line. When one of the memory cells is selected so that the potential on one of the complementary bit lines associated with the particular cell declines, the current path provided through one of these two series combinations of transistors also declines until the current path is blocked with one of the transistors forming the particular transistor combination turned off. A considerably large amount of current is thus allowed to path through one combination of transistors in addition to the current which passes through the other combination of transistors until the current path formed by the former is blocked. This gives rise to an increase in the amount of power dissipation by the memory device.
It is accordingly a prime object of the present invention to provide an improved sense amplifier circuit in which the current allowed to flow through the amplifier circuit during each cycle of operation of the circuit is significantly reduced at an early point of time during the cycle of operation.